U.S. President Donald Trump’s first overseas trip will begin in Saudi Arabia and Israel, two countries whose leaders have vocally welcomed Trump’s shift in approach to the region compared to his predecessor, Barack Obama. But the new president’s unpredictable nature means that neither country can take anything for granted during his visit.

The White House has previewed the president’s trip, which will also take him to Italy for the G-7 Summit in Sicily and a meeting with the Pope, and Brussels for the NATO Summit. Trump’s national security adviser, Lt. Gen. H.R. McMaster, briefed the press Friday, outlining an ambitious program with three themes: to reaffirm American leadership, to bond with world leaders, and to promote a message of unity among three of the world’s great religions, Judaism, Islam and Christianity. More specifically, the president is expected to engage his counterparts in the Middle East on containing Iran, countering the so-called Islamic State and al-Qaida, and promoting the Israel-Palestine peace process. ...